The reaction of an ester $RCOOR'$ with an alcohol $R''OH$ in the presence of an acid gives

Identify the reagent used in the following reaction.
Benzoic acid $\xrightarrow{\text{Reagent}}$ Benzoyl chloride $+$ Phosphorus oxychloride $+$ Hydrogen chloride

Identify the product $B$ in the following reaction sequence:
$C_6H_5COOH$ $\xrightarrow{NaOH} A$ $\xrightarrow{\text{Electrolysis}} B$

The compound $(X)$ in the given reaction is:
$MeO-C_6H_4-CHO + (X) \xrightarrow{CH_3COONa, H_3O^+} MeO-C_6H_4-CH=CHCOOH$

The product $(D)$ in the following reaction sequence is: $HOCH_2CH_2CH_2COOCH_2CH_3$ $\xrightarrow{PCC} (A)$ $\xrightarrow[{(1 \ molar \ equivalent)}]{H_2C=CHMgBr} (B)$ $\xrightarrow{NH_4Cl/H_2O} (C)$ $\xrightarrow[H_2O]{KOH}$ $\xrightarrow{H_3O^{+}}$ $\xrightarrow[pyridine]{(CH_3CO)_2O} (D)$

Propionic acid with $Br_2/P$ yields a dibromo product. Its structure would be: